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As the flood of data across the internet continues to increase, there are those that say sometime soon it is going to collapse under its own weight. But that is what they said last year.

Web traffic in the 90s was much smaller than today

Back in the early 90s, those of us that were online were just sending text e-mails of a few bytes each, traffic across the main US data lines was estimated at a few terabytes a month, steadily doubling every year.

But the mid 90s saw the arrival of picture-rich websites, and the invention of the MP3. Suddenly each net user wanted megabytes of pictures and music, and the monthly traffic figure exploded.

For the next few years we saw more steady growth with traffic again roughly doubling every year.

But since 2003, we have seen another change in the way we use the net. The YouTube generation want to stream video, and download gigabytes of data in one go.

"In one day, YouTube sends data equivalent to 75 billion e-mails; so it's clearly very different," said Phil Smith, head of technology and corporate marketing at Cisco Systems.

"The network is growing up, is starting to get more capacity than it ever had, but it is a challenge.

"Video is real-time, it needs to not have mistakes or errors. E-mail can be a little slow. You wouldn't notice if it was 11 seconds rather than 10, but you would notice that on a video."

Spending our inheritance

Perhaps unsurprisingly, every year someone says the internet is going to collapse under the weight of the traffic.

The net's backbone was built thanks to the 90s dotcom boom

Looking at the figures, that seems a reasonable prediction.

"Back in the days of the dotcom boom in the late 90s, billions of dollars were invested around the world in laying cables," said net expert Bill Thompson.

"Then there was the crash of 2000 and since then we've been spending that inheritance, using that capacity, growing services to fill the space that was left over by all those companies that went out of business."

Router reliability

Much more high-speed optic fibre has been laid than we currently need, and scientists are confident that each strand can be pushed to carry almost limitless amounts of data in the form of light.

But long before a backbone wire itself gets overloaded, the strain may begin to show on the devices at either end - the routers.

"If we take a backbone link across the Atlantic, there're billions of bits of data arriving every second and it's all got to go to different destinations," explained Mr Thompson.

The real issue that people are going to face, and are already noticing at home, is that ISPs are starting to cut back on the bandwidth that is available to people in their homes

Bill Thompson, net expert

"The router sits at the end of that very high speed link and decides where each small piece of data has to go. That's not a difficult computational task, but it has to make millions of decisions a second."

The manufacturer of most of the world's routers is Cisco. When I pushed them on the subject of router overload, they were understandably confident.

"Routers have come a long way since they started," said Mr Smith. "The routers we're talking about now can handle 92 terabits per second.

"We have enough capacity to do that and drive a billion phone calls from those same people who are playing a video game at the same time they're having a text chat."

Congestion

Even if the routers can continue to take what the fibre delivers, there is another problem - the internet is not all fibre.

A lot of the end connections, the ones that go to our individual home computers, are made of decades-old copper.

"The real issue that people are going to face, and are already noticing at home, is that ISPs are starting to cut back on the bandwidth that is available to people in their homes," said Mr Thompson. "They call it bandwidth shaping.

"They do this because they have a limited capacity to deliver to 100 or 200 homes, and if everybody's using the internet at the same time then the whole thing starts to get congested. Before that happens they cut back on the heavy users."

Obstacles

But digital meltdown is not the only threat facing the net. There are other, more sudden, real world hazards which the net has to protect against.

Anything from terror attacks to, would you believe it shark bites, can and have taken out major links and routers.

It only takes an earthquake, as we saw at the end of last year, to take out a significant segment of internet infrastructure

Paul Wood, MessageLabs

"There's a perception that the internet is very resilient," said Paul Wood, senior analyst of security firm MessageLabs. "The way it was designed means that if any particular part of it is disrupted then the traffic will find another route.

"It only takes an earthquake, as we saw at the end of last year, to take out a significant segment of internet infrastructure. Then the traffic finds another route, but it goes over a very slow route, which then becomes saturated and can't handle the bandwidth. Then you lose the traffic and that part of the world goes dark for a while."

For decades the internet has kept pace with our demands on it. And demand continues to grow.

And the service providers will continue to insist that the net will survive, and the doomsayers will continue to insist that it is just about to collapse.